Whiplash related injuries are caused by the rapid acceleration of a person's cranium and cervical spine, which occurs, for example, in a rear end automobile collision. The rapid acceleration causes the extension and flexion of the cervical spine which, in turn, can cause severe injury. Types of whiplash related injuries include fractured and/or dislocated vertebrae, torn ligaments (both anterior and posterior of the spinal column), and avulsion of parts of the vertebrae, ligaments and intervertebrae discs. Similar injuries can occur to the thoracic and lumbar spinal areas.
It has thus been found, for example, that the C4, C5 and C6 cervical vertebrae, and the paravertebrae ligaments are most often damaged with whiplash related injuries, although the entire cervical as well as the thoracic and lumbar spine may well be involved. Rapid hyperextension of the cervical spine can thus stretch the anterior longitudinal ligament, thus placing it in traction and causing either bone or ligamentous damage. Such hyperextension typically damages the C1 through C7 cervical vertebrae. The vertebral artery, which extends through an opening in the vertebrae, and the sympathetic nerve fibers that surround the artery are also often damaged. These types of injuries cause severe disabilities and, in some instances, death.
Seatbacks and/or headrests in automobiles, trucks, and other types of vehicles are provided to prevent whiplash related injuries to passengers during collisions, but typically fail. During a rear-end vehicle collision, the forces of the collision typically cause a passenger's cranium and cervical spine to rapidly accelerate toward the rear of the vehicle. Once the cranium strikes the seatback or headrest, it then rapidly accelerates in the opposite direction toward the front of the vehicle. The rearward acceleration of the cranium, and resulting collision with the seatback or headrest, causes hyperextension of the cervical spine and, thus typically injures the anterior structure of the passenger's neck. The forward acceleration of the cranium, on the other hand, causes hyperflexion of the cervical spine and typically injures the posterior structure of the neck.
One problem with known seatbacks and/or headrests is that the surface intended to stop the movement of a person's head and neck is typically flat, or does not correspond to the posterior contour thereof. As a result, during a rear-end collision, typically the back, or posterior portion of the cranium is the first portion of the passenger's body to strike the seatback or headrest. However, the cervical spine, which is located inferiorly with respect to the posterior portion of the cranium, continues to move toward the headrest. As a result the cervical spine is forced to move relative to the cranium which, in turn, causes severe vertebral damage.
Also, the top surfaces of many known headrests are located at about the same height, or below the height of a passenger's ears, which is normally about the center of gravity of the head. When a passenger's cranium is forced against such a headrest during a collision, it often slides upwardly over the top edge of the headrest. As a result, the cranium is stretched upwardly relative to the cervical spine, typically causing further vertebral damage.
In my issued U.S. Pat. Nos. 5,181,763 and 5,290,091, the entire disclosures of which are hereby incorporated by reference, apparatus is disclosed for preventing whiplash-related injuries to a passenger in a vehicle. In one embodiment of these inventions, the apparatus comprises a frame supported on a seat of the vehicle and located behind the cranium and cervical spine of a passenger on the seat. A layer of resilient material is supported on the frame, the layer of resilient material defining a supporting means located behind the cranium and cervical spine of the passenger and defining one or more contours that interfit with the posterior contour of the passenger's cranium and cervical spine. The supporting means includes a first surface located behind the passenger's cranium and projecting upwardly above the approximate center of mass of the passenger's cranium and having a substantially flat portion including a cranium contact zone for contacting and supporting the approximate central posterior area of the passenger's cranium; and a second surface located below the first surface and defining a substantially convex smooth curve, the maximum protrusion point of which projects anteriorly relative to the flat portion of the first surface. The second surface thereby contacts and supports the posterior portion of the passenger's cervical spine substantially simultaneously with the contact of the passenger's cranium with the first surface, thereby substantially simultaneously decelerating the cranium and cervical spine during a vehicle collision to prevent whiplash-related injuries to the passenger.
In such prior invention, the second surface is smoothly joined to the first surfaces by a transition surface which extends anteriorly at an obtuse angle from the first surface and is located to support the passenger's posterior area approximately where the cranium meets the cervical spine.
A support member is coupled to the frame and supported on the seat, the support member being vertically moveable relative to the seat to adjust the position of the apparatus relative to the passenger and, thus, adjust the position of the supporting means to correspond to the posterior contour of the passenger's cranium and cervical spine.
The frame can define a hollow enclosure and the layer of resilient material may consist essentially of a urethane foam which is molded thereon.
The frame is journaled to the support member and normally biased toward the front of the seat, whereupon during a vehicle collision, when the passenger's head is forced toward the apparatus, the posterior portion of the passenger's cranium initially contacts the first surface of the supporting means and rotates the frame relative to the support member toward the back of the seat and, in turn, rotates the second supporting surface into contact with the posterior portion of the passenger's lower cranium and cervical spine.
In a further embodiment of our prior apparatus, the first and second surfaces are defined at mutually spaced first and second support bodies, and the apparatus further includes means for vertically and horizontally displacing the first and second surfaces to adjust the position of same to accurately interfit with the posterior contour of different passengers.
The first and second support bodies can be coupled to the frame and rendered movable by rack and pinion or equivalent means to enable desired vertical and/or horizontal displacements of same.
It may be noted in the foregoing discussions, that the construction of most prior art seatbacks and head rests incorporate materials that in an effort to provide maximum comfort, are highly resilient. Such materials while they may absorb some of the impact energy which is generated as the passenger is thrown rearwardly against the seat during a rear end impact, promptly transfer the absorbed energy back to the passenger, causing a rebound effect, which only adds to the detrimental conditions which foster injury.
In accordance with the foregoing, it may be regarded as an object of the present invention, to overcome the problems and disadvantages of known apparatus for preventing whiplash, such as vehicle headrests and seatbacks.
It is a further object of the present invention, to provide apparatus of the foregoing type, which includes means for efficiently and safely absorbing impact energy, thereby further diminishing the likelihood of passenger injury.